Search

This paper presents a review of recent advances in modeling and simulation of conventional metal machining processes, which continue to dominate a significant part of all machining processes, and in recent years, the need for predictive models for machining processes has grown in importance in the digital manufacturing age. Significant advances have been made in modeling the mechanics of cutting in conventional machining, driven by industrial need and enabled by rapid advances in computational power. The paper surveys the state-of-the-art in analytical and numerical modeling of conventional metal machining processes with a focus on their ability to predict useful performance attributes including chip geometry, forces, temperatures, tool wear, residual stress, and microstructure. Also included in the review is a discussion of the industrial use of modeling and simulation tools for conventional machining. Additionally, the practical applicability, implementation benefits, and methodological limitations of conventional machining process modeling have been examined. The paper concludes with a summary of future research directions in modeling and simulation of conventional metal machining processes. [ABSTRACT FROM AUTHOR]

Brittleness in paper is one of the primary reasons library books are removed from circulation, digitized, or have their access limited. Yet, paper brittleness is difficult to characterize as it has multiple definitions and no single measurable physical or chemical property associated with it. This study reevaluates the cantilever test as applied to aged papers. In this nondestructive test, the deflection of a strip of paper held horizontally is measured across its length. The deflection data are then fit to nonlinear bending theories assuming large deflection of a cantilever beam under a combined uniform and concentrated load. Fitting the shape of the deflection profiles provides bending and elastic moduli, the bending length, and confirms that the paper sheets respond linearly. The results are compared to those calculated from a simplified single point measurement of the maximum deflection of the cantilevered sample. Young's modulus measured by the cantilever test is lower for paper-based materials than that measured by tensile testing, and the bending modulus was found to correlate with the destructive Massachusetts Institute of Technology (MIT) fold endurance test. [ABSTRACT FROM AUTHOR]

The extended meniscus and the intermolecular and capillary forces that govern its behavior and connection to change-of-phase heat transfer have been the subject of an increasing body of research over the past 50 years. We have been fortunate to be at the forefront of this effort starting from the development of a capillary feeder, in Earth's gravity, to stabilize film boiling to running a series of transparent heat pipe experiments aboard the International space station hoping to better understand the role of intermolecular forces in microgravity. The use of ellipsometry and interferometry to highlight the location and state of the vapor-liquid interface have been key to these studies and have helped to uncover many new, interesting, and sometimes unexpected phenomena associated with fluid flow and change-of-phase heat transfer. [ABSTRACT FROM AUTHOR]

Compares two advanced gas turbine types integrated with the combined cycle, steam injected gas turbine (STIG) and evaporative gas turbine (EvGT), in pulp and paper mills for increased power generation. STIG Cycle and its application in pulp and paper industry; EvGT Cycle; Reference pulp and paper mills; Modeling of advanced gas turbine systems.

Presents information on a study which analyzed the heating and drying process of moist paper with infrared radiation energy. Set-up of the experiment; Description of paper samples; Error and theoretical analyses; Results of the study; Comparison of numerical and experimental results.

Fouling afflicts gas turbine operation from first time application. Filtration systems and washing operations work against air contaminants in order to limit the particles entering the compressor inlet and remove the existing deposits. In this work, a global overview of the operational experience of the manufacturer, the filtration systems, and the particle deposition of the compressor are reported. The data reported in this review have been collected from 60 years (1956-2015) of ASME Turbo Expo proceedings. This conference is recognized as the must-attend event for turbomachinery professionals. Through the years, many issues have been resolved by the contributions of this conference. Regarding the compressor fouling phenomenon, the contributions presented at the ASME Turbo Expo mark the high level of development in this field of research, thanks to the simultaneous presence of manufacturers, government, and academia attendees. The goal of the authors is to describe the technological evolution and challenges faced by manufacturers and researchers through the years, highlighting the state of the art in the knowledge of fouling, and defining the background on which further studies will be based. [ABSTRACT FROM AUTHOR]

It was an honor to receive the Max Jakob Memorial Award for 2018. This invited paper is based on the award lecture and is written in an informal style expanding on the lecture and focusing on work in which I have been involved over the past 60-years. Early experimental and theoretical work was published only in conference proceedings when this was regarded an alternative to a journal and not, as seems to be the case nowadays, prior to journal publication or for incomplete work. I welcome this opportunity to clarify and make some of this earlier work more readily accessible. My comments on more recent work of others are also included. [ABSTRACT FROM AUTHOR]

Carbon-fiber-reinforced paper-based friction material (CFRPF), as a new type of wet friction material for automatic transmission, was prepared by a paper-making process. The frictional response of CFRPF is highly complex under a set of dynamically variable operating conditions. To better understand the effect of operating factors (braking pressure, rotating speed, oil temperature, and oil flow rate) on friction stability of the material, tests were carried out using a single ingredient experiment and the Taguchi method. Experimental results show that the braking stability and the dynamic friction coefficient ([[mu].sub.d]) decrease as braking pressure, rotating speed, oil temperature, and oil flow rate increase. The influence of braking pressure on [[mu].sub.d] is largest among the four operating factors. [[mu].sub.d] declines gradually during the first 3000 repeated braking cycles and changes very little subsequently due to the surface topography change in friction material. Keywords: paper-based friction material, carbon fiber, friction torque curve, dynamic friction coefficient

Oil-free microturbomachinery (OFT) implements compliant foil bearings because of their minute drag and ability to operate in extreme (high or low) temperature. Prominent to date, bump-foil thrust bearings integrate an underspring thin metal structure that provides resilience and material damping, and while the rotor is airborne, it acts in series with the stiffness and damping of the gas film. The design and manufacturing of foil bearings remain costly as it demands extensive engineering and actual experience. Alternative foil bearing configurations, less costly and easier to manufacture, are highly desirable to enable widespread usage of OFT. This paper details the design and manufacturing of a novel Rayleigh-step metal mesh foil thrust bearing (MMFTB) as well as its testing on a dedicated rig. Metal mesh structures offer significant material structural damping and can be easily procured at a fraction of the cost of a typical bump-foil strip layer. The MMFTB consists of a solid carrier, a number of stacked annular copper mesh sheets (wire diameter = 0.25, 0.3, and 0.41 mm), and a steel top foil (0.127 mm thick) that makes six pads (ID = 50.8 mm, OD =2 ID), each 45 deg in extent. A 3 μm polymer coats each pad, and a photochemical process etches a step 20 μm in height. Static and dynamic load measurements (without rotor speed) demonstrate that the MMFTB has structural stiffness and material damping similar to that of a publicized bump-type foil thrust bearing. A maiden test of the MMFTB with rotor speed of Ω = 15 krpm (~80 m/s at bearing outer diameter (OD)) proved briefly the bearing operation when applying a tiny thrust load. Further tests with ambient air, a rotor speed of 40 krpm (~212 m/s at bearing OD), and a very light load/area <7 kPa failed several of the prototype bearings, all exhibiting significant wear on one or more pads. The source of the failure is the inherent unevenness of the metal mesh stacked substructures, thus causing the pads to bulge toward the rotor collar surface before a load applies. A deficient anchoring method exacerbates the unevenness. Incidentally, a high rotor speed induced large windage that lifted the top foils pushing them against the spinning collar. As the bearing moved toward the rotating collar to begin applying thrust, the local high spots rubbed against the collar before a hydrodynamic wedge could form to separate the surfaces. Without a robust sacrificial coating, metal-to-metal contact quickly disfigured the contacting top foil pads, erasing the etched step, and leading to failure. In concept, and on paper, the mesh sheets and the top foil lay flat against the bearing carrier, giving a false sense of uniformity in the design process. In actuality, a designer must consider the manufactured states of the individual components and how they assemble. A redesign of the bearing intends to overcome the existing flaws (highlighted herein) by incorporating a thicker top foil that is well anchored (to better withstand the effects of windage), a robust sacrificial coating, and a hydrodynamic wedge accomplished via a circumferential taper on each pad. [ABSTRACT FROM AUTHOR]

In order to improve the precision of machining and reduce the processing cost of paper honeycomb core, a new method is presented to fix the honeycomb cote work piece to the working platform using magnetic and frictional forces. In this method, iron powder is used as a medium instead of the traditional adhesive-based material to achieve the bonding between the work piece and the working platform. Iron powder is poured into honeycomb cells until it reaches the desired height using a numerically controlled iron powder feeder system. In addition, a magnetic working platform is manufactured and placed on top of the station of the milling machine. The magnetic field produced by the magnetic working platform is leaded to the iron powder while the magnetic field control system switches on. More precisely, the mutual magnetic attraction between the iron powders located in different cells of the honeycomb and between the iron powder and the platform is generated. While cutting force is applied to the work piece, two types of friction force occur. One is between the iron powder and the wall of the honeycomb cells, and other one is between the work piece and the working platform. Once the resultant friction force balances the machining load, the work piece will be then fixed to the platform. In this paper, a new bonding system based on the new method is introduced and demonstrated. [DOI: 10.1115/1.2039944]

Origami is the art of creating a three-dimensional (3D) shape by folding paper. It has drawn much attention from researchers, and the designs that origami has inspired are used in various engineering applications. Most of these designs are based on familiar origami patterns and their known deformations, but origami patterns were originally intended for materials of near-zero thickness, primarily paper. To use the designs in engineering applications, it is necessary to simulate origami in a way that enables designers to explore and understand the designs while taking the thickness of the material to be folded into account. Because origami is primarily a problem in geometric design, this paper develops a geometric simulation for thick origami. The actuation, constraints, and assignment of mountain and valley folds in origami are also incorporated into the geometric formulation. The experimental results show that the proposed method is efficient and accurate. The method can successfully simulate a flat-foldable degree-four vertex, two different action origami, the bistable property of a waterbomb base, and the elasticity of non-rigid origami panels. [ABSTRACT FROM AUTHOR]

Carbon-fiber-reinforced paper-based friction material (CFRPF), as a new type of wet friction material for automatic transmission, was prepared by a paper-making process. The frictional response of CFRPF is highly complex under a set of dynamically variable operating conditions. To better understand the effect of operating factors (braking pressure, rotating speed, oil temperature, and oil flow rate) on friction stability of the material, tests were carried out using a single ingredient experiment and the Taguchi method. Experimental results show that the braking stability and the dynamic friction coefficient (μd) decrease as braking pressure, rotating speed, oil temperature, and oil flow rate increase. The influence of braking pressure on μd is largest among the four operating factors. μd declines gradually during the first 3000 repeated braking cycles and changes very little subsequently due to the surface topography change in friction material. [ABSTRACT FROM AUTHOR]

To understand the response of Alloy 617 to long-time exposure conditions and to determine the supplementary data needs for structural components in Gen IV nuclear reactors, literature of aging and aging effects in the alloy was reviewed. Most of the reviewed data were produced in connection with the international research effort supporting high temperature gas-cooled reactor projects in the 1970s and 1980s. Topics considered included microstructural changes, hardness, tensile properties, toughness, creep-rupture, fatigue, and crack growth. It became clear that, for the long-time very high-temperature conditions of the Gen IV reactors, a significant effort would be needed to fully understand and characterize property changes. Several topics for further research were recommended. [DOI: 10.1115/1.2967885]

No abstract.

The Journal of Biomechanical Engineering has contributed to biomechanical engineering field since 1977. To honor papers published at least 30 years that have had a long-lasting impact on the field, the Editors now recognize "Legacy Papers." The journal is pleased to present the following paper as this year's Legacy Paper: "A New Simplified Bioheat Equation for the Effect of Blood Flow on Local Average Tissue Temperature" by S. Weinbaum and L. Jiji, ASME Journal of Biomechanical Engineering 107: 131-139, 1985.

The paper describes the development and description of the aerodynamic models used to estimate the aerodynamic loads on wind turbine constructions. This includes a status of the capabilities of compulation fluid dynamics and the need for reliable airfoil data for the simpler engineering models. Also a discussion of the use of passive and active aerodynamic devices is included such as, e.g.. Vortex Generators and distributed active flaps. Finally the problem of wakes in wind farms is addressed and a section of the likely future development of aerodynamic models for wind turbines is included. [ABSTRACT FROM AUTHOR]

To understand the response of Alloy 617 to long-time exposure conditions and to determine the supplementary data needs for structural components in Gen IV nuclear reactors, literature of aging and aging effects in the alloy was reviewed. Most of the reviewed data were produced in connection with the international research effort supporting high temperature gas-cooled reactor projects in the 1970s and 1980s. Topics considered included microstructural changes, hardness, tensile properties, toughness, creep-rupture, fatigue, and crack growth. It became clear that, for the long-time very high-temperature conditions of the Gen IV reactors, a significant effort would be needed to fully understand and characterize property changes. Several topics for further research were recommended. [ABSTRACT FROM AUTHOR]

Presents information from a test on the effects of visco-elastic property on friction characteristics of paper-based friction materials for oil immersed clutches. Materials used in the test; Information on friction materials for oil immersed clutches in automobile automatic transmission; Results of test.

Presents a theory on frictional vibrations of paper-based friction material considering the interaction between its deformation and the consequent lubricant flow inside it. Vibration model; Derivation of stability criterion; Relation between negative damping components in critical state; Contribution of each parameter to stability.

The article announces the winners of the 2016 Summer Biomechanics, Bioengineering, and Biotransport Conference Student Paper Competition including John P. Carruth, Sonia Kartha, and Jack A. Martin.

Fluid injection is a common practice in the oil and gas industry found in many applications such as waterflooding and disposal of produced fluids. Maintaining high injection rates is crucial to guarantee the economic success of these projects; however, there are geomechanical risks and difficulties involved in this process that may threat the viability of fluid injection projects. Near wellbore reduction of permeability due to pore plugging, formation failure, out of zone injection, sand production, and local compaction are challenging the effectiveness of the injection process. Due to these complications, modeling and simulation has been used as an effective tool to assess injectors' performance; however, different problems have yet to be addressed. In this paper, we review some of these challenges and the solutions that have been proposed as a primary step to understand mechanisms affecting well performance. [ABSTRACT FROM AUTHOR]

Over the past few decades, folding paper has extended beyond the origami deployable applications to reach the engineering field. Nevertheless, mechanical information about paper behavior is still lacking, especially during folding/unfolding. This article proposes an approach to characterize the paper fold behavior in order to extract the material data that will be needed for the simulation of folding and to go a step further the single kinematics of origami mechanisms. The model developed herein from simple experiments for the fold behavior relies on a macroscopic local hinge with a nonlinear torsional spring. Though validated with only straight folds, the model is still applicable in the case of curved folds thanks to the locality principle of the mechanical behavior. The influence of both the folding angle and the fold length is extracted automatically from a set of experimental values exhibiting a deterministic behavior and a variability due to the folding process. The goal is also to propose a methodology that may extend the simple case of the paper crease, or even the case of thin material sheets, and may be adapted to other identification problems. [ABSTRACT FROM AUTHOR]

The article offers information on the Student Paper Competition at the 2015 Summer Biomechanics, Bioengineering, and Biotransport Conference in the U.S. Topics discussed include an overview of the competition, the technical areas of the competition, the variety of awards given, and the winners of the competition's categories such as in bachelor's degree, master's degree and doctoral degree.

The purpose of this brief paper is to present a new derivation of Biot 's theory of linear poroelasticity (Biot, M., 1935, "Le Probleme de la Consolidation des Matieres Argileuses Sous une Charge," Ann. Soc. Sci. Bruxelles, B55, pp. 110-113; Biot, M., 1941, "General Theory of Three-Dimensional Consolidation," J. Appl. Phys., 12, pp. 155-164; and Biot, M., and Willis, D., 1957, "The Elastic Coefficients of the Theory of Consolidation," J. Appl. Mech., 24, pp. 594-601) in a modern thermodynamically consistent fashion, and show that it may be deduced as a special case of a more general theory of chemoelasticity. [ABSTRACT FROM AUTHOR]

The dependence of the fracture toughness of two-dimensional (2D) elastoplastic lattices upon relative density and ductility of cell wall material is obtained for four topologies: the triangular lattice, kagome lattice, diamond lattice, and the hexagonal lattice. Crack-tip fields are explored, including the plastic zone size and crack opening displacement. The cell walls are treated as beams, with a material response given by the Ramberg-Osgood law. There is choice in the criterion for crack advance, and two extremes are considered: (i) the maximum local tensile strain (LTS) anywhere in the lattice attains the failure strain or (ii) the average tensile strain (ATS) across the cell wall attains the failure strain (which can be identified with the necking strain). The dependence of macroscopic fracture toughness upon failure strain, strain hardening exponent, and relative density is obtained for each lattice, and scaling laws are derived. The role of imperfections in degrading the fracture toughness is assessed by random movement of the nodes. The paper provides a strategy for obtaining lattices of high toughness at low density, thereby filling gaps in material property space. [ABSTRACT FROM AUTHOR]